134 THE CONNECTIVE TISSUES, BY A. EOLLETT. 



which, however, small roundish coarsely granulated cells are 

 distributed. In this last tissue well-developed blood-vessels 

 are clearly visible. 



Thus in the cavities of calcified cartilage there appears in the 

 first instance a new soft material composed of numerous cells, 

 of which the superficially situated are differentiated from those 

 that occupy the interior. 



The question now arises, from whence do these tissues origi- 

 nate ? It is to be remarked that the limits between the large- 

 celled region of the cartilage, and the subsequently formed con- 

 tents of the spaces bounded by the calcified trabeculse, are very 

 sharply defined in all the preparations I have examined. I 

 have never been able to discover any transitional stages between 

 the large clear cartilage cells and the dark coarsely granular 

 cells which suddenly make their appearance. Such transi- 

 tional stages might, however, be expected to occur frequently 

 if the cartilage cells constituted mother cells, giving origin to 

 those of the medulla by fission. However high, therefore, may 

 be the authorities by which the latter view is supported, I must 

 still doubt its accuracy. It is indeed conceivable that processes 

 of division may here occur with such rapidity as to be con- 

 cealed from the eye of the observer, and thus lead us to grant 

 the development of the medulla from the cartilage cells, as a 

 convenient theory, though unsupported by direct observation. 

 We are certainly, however, not compelled to admit this view, 

 since there is no difficulty in supposing the medulla to shoot 

 into the cartilage from the same surface as that from which the 

 blood-vessels emanate. This last view is especially supported 

 by the circumstance that, as we shall see, an analogous pro- 

 ductive activity must necessarily be attributed to the medulla, 

 and will hereafter be traced in it. 



The productive activity of the cartilage cells appears to me 

 to cease at the limits of the flat-celled region. The large vesi- 

 cular cells which extend from this point to the plane of ossifi- 

 cation may frequently be seen where the medulla commences, 

 in a state of finely granular atrophy, similar to that of the car- 

 tilage matrix itself, so that only the remains of these cells are 

 found in the medulla. 



The view here given at length must not be confounded with 



